Pneumatic differential pressure amplifier

ABSTRACT

A differential amplifier in which two balls of the same diameter are displaceable in a housing bore and control at least one outlet channel, whereby the supply channel for compressed air is disposed in the housing substantial in line with the point of contact between the two balls when the difference in pressure is zero, and at a distance from the outlet channel equal to half the diameter of a ball.

United States I Patent Bader [54] PNEUMATIC DIFFERENTIAL PRESSUREAMPLIFIER [72] Inventor: Horst Bader, Stuttgart-Fasanenhof,

Germany [73] Assignee: J. C. Eckardt AG., Stuttgard, Germany [22] Filed:Oct. 28, 1970 [21] App1.N0.: 84,630

[30] Foreign Application Priority Data Nov. 3, 1969 Germany ..P 19 55083.5

[52] US. Cl. ..137/625.48, 137/815, 235/201 ME [51] Int. Cl. ..F16k11/02, F150 3/04, Fl5c 3/06 [58] Field of Search ..137/62547, 625.48,81.5;

[56] References Cited UNITED STATES PATENTS 3,384,122 5/1968 Harpman..251/367 [151 3,682,199 [4 1 Aug. 8, 1972 3,227,180 1/ 1966Tissot-Dupont ..251/367 X 3,311,301 3/1967 Chabrier et al. ....235/201ME 3,319,885 5/1967 Eige ..235/201 ME 3,326,239 6/1967 Saint-Joanis eta1 ,.235/201 ME 3,335,950 8/1967 Tal et a1 235/201 ME 3,362,633 1/1968Freeman ..235/201 ME Primary Examiner-Samuel Scott Attorney-Craig,Antonelli, Stewart & Hill [57] ABSTRACT A differential amplifier inwhich two balls of the same diameter are displaceable in a housing boreand control at least one outlet channel, whereby the supply channel forcompressed air is disposed in the housing substantial in line with thepoint of contact between the two balls when the difierence in pressureis zero,

and at a distance from the outlet channel equal to half the diameter ofa ball.

8 Claims, 5 Drawing Figures Patented Aug. 8, 1972 3,682,199

1N VENTOR H ORST BADE R BY Cvait AatQngLLL, Stewart: qr ATTORNEYS Theinvention relates to a pneumatic differential pressure amplifierconsisting of two resilient walls (diaphragms, spring bellows, capsulesprings) which unilaterally bound two input pressure chambers and serveas an adjusting arrangement for the adjustment of balls which controlthe inlet and outlet of compressed air. Prior art differential pressureamplifiers generally have two pressure bellows which act on a leversystem, the movement of which, dependent upon the difference between thepressures in the bellows, is used to modulate a system of nozzle plates.Differential pressure amplifiers of this type require a certain amountof space which must be regarded as an absolute minimum. In ad- 'dition,they are relatively involved and costly and do not permit of a compactconstruction. Furthermore, a power amplifier must generally be disposeddownstream of the prior art differential pressure amplifiers, since thenozzle plate system can only provide a relatively small quantity of air.

Furthermore, a construction of differential pressure amplifiers is knowin which four balls are necessary to control the inlet and outlet ofpressurized medium, as well as bores of different diameter. In thiscase, two balls are displaceable in one control bore, the length ofwhich must be accurately observed if reversing errors are to be avoidedor kept to the minimum. In addition, the distance between these controlbores must also be made with a small tolerance. This signifiesconsiderable complication and expenditures in the manufacture of theseknown differential pressure amplifiers. By virtue of the manner in whichthese amplifiers operate, two balls in each case leave their controlbore and are no longer laterally guided. This has an adverse effect onthe functional reliability and gives rise to properties which depend onthe position of the amplifier.

The present invention is based on the problem of avoiding thesedisadvantages and of providing a differential pressure amplifier whichcan be manufactured and constructed easily and space-savingly and thesensitivity of which can be increased as compared with knowndifferential pressure amplifiers. In the case of differential pressureamplifiers of the type mentioned hereinabove, the present inventionessentially resides in that the resilient walls are in operativecommunication with two balls of the same diameter disposed fordisplacement in a bore in the casing of the amplifier and of constantdiameter disposed for displacement in a bore in the casing of theamplifier and of constant diameter, and in that a compressed air supplyduct is disposed in line with the point of contact of the balls, and inthat at least one outlet duct is provided which discharges into the boreat a distance of half the diameter of the ball from the supply duct.

The present invention makes it possible to dispense with lever systems.The movement of the diaphragms or bellows is used directly to move twoballs, at least one of which more or less opens or closes an outletduct. The sensitivity and degree of amplification of the amplifier isincreased if two balls serve as throttle members which control theoutflow of compressed air into one respective outflow duct each.

- It is envisaged that the balls bear on or abut against each other andthat the supply duct for the pressure medium is located approximately inline with the point of contact between the balls. With such aconstruction, each ball with its corresponding outlet duct acts as avariable throttle resistance, and more particularly in the reversedirection to one another, i.e., when one ball opens up its outlet ductand enables the discharge of pressure medium, then the other ball at thesame time closes to an ever increasing degree the outflow duct which isassociated with it. The outlet signal in the first outlet duct thereforerises while the outlet signal in the second outlet duct drops. Bychoosing the same crosssections, it is possible to ensure that thepressure in one outlet duct drops to the same extent as it rises in theother outlet duct so that, when the difference between output signals ismeasured in the output of the differential pressure amplifier, adoubling of the amplification factor is in theory attainable.

The differential pressure amplifier according to the inventionrepresents a space-saving and operationally reliable construction.During operation, only two balls are displaced and guided in a bore ofconstant diameter. The length of this bore is not subject to any closetolerances. Only the spacing between the outlet ducts and the air supplyduct must be respected. It offers no notable difficulty to observe andcontrol these dimenslons.

In order to achieve the same flow conditions at the throttle stations,it is envisaged that the balls be of the same diameter and be gilded ina common bore, whereby for structural reasons a bore in a cylinderinserted into a housing is appropriately provided to guide the ballswhich is slotted laterally to increase the outflow duct cross-section.For each outlet duct, the cylinder may also be horizontally slotted atboth ends and may be provided, for the supply of pressure medium, with abore extending at right-angles to the outlet duct connections adjoiningthe slots.

The sensitivity and air output of the differential pressure amplifiercan be enhanced by this measure. Small reciprocating movements of thestill laterally guided throttle members (balls) will produce a greaterchange in the outflow cross-sections.

Since the cylindrical piece can be machined before it is inserted intothe housing, it can be manufactured without difficulty. Naturally, it isalso possible to provide for both outlet ducts different throttlingcurves or throttle cams if this should be desired.

The invention will be explained in greater detail hereinafter withreference to some embodiments illustrated in the attached drawings, inwhich:

FIG. 1 is an axial cross-section through a schematically illustrated,exemplary embodiment of a differential pressure amplifier according tothe present invention;

FIG. 2 is a cross-section taken along the line Il-II in FIG. 1, lookingin the direction of the arrows;

FIG. 3 is a cross-section, similar to FIG. 2, of a second embodiment ofa pressure amplifier according to the invention;

FIG. 4 is a diagrammatic view of the novel differential pressureamplifier to explain its mode of operation, and

FIG. 5 is a diagram showing the pattern of the two output signals of thenovel amplifier as a function of the differential pressure acting on theamplifier.

According to the invention, a pneumatic differential pressure amplifiercomprises :two resilient walls each of which forms one wall of an inputpressure chamber and serves as an adjusting arrangement for an adjustingball valve, each of which controls the inlet and outlet of compressedair into and out of an outlet duct, wherein the resilient walls are eachin operative communication with one of two balls of the same diameterdisposed to be displaceable in a bore of constant diameter in thehousing of the amplifier, a compressed-air supply duct is alignedtangentially aligned with the point of contact of the balls 4 in thisposition, there is provided in the cylinder 2 and in the adjacenthousing 1 a bore 7, through which compressed air is supplied at thesupply pressure 2,. Also contained in the housing 1 are two furtheroutlet bores 8 and 9, at which the output signals A and A can bedetected and measured. The bores 8 and 9 start with conicallyconstructed slots 10 in the cylinder 2 which serve to increase theoutlet cross-section for the compressed air upon movement of the balls4, so that a high degree of sensitivity and air output can be achieved.

In order further to increase the outlet cross-section and therewith toimprove the flow conditions and enhance the sensitivity, it is alsopossible, according to FIG. 3 to provide for each output signal a doublepickup by means of the arms 8a at the cylinder 2 provided on both sideswith slots 10a. In this case, the pressurized medium p, must be suppliedthrough the bore 7a approximately at right-angle to the end of the arms8a. FIG. 3 shows the arrangement for the output signal A theconstruction for the output signal A, is similar but as in FIG. 1staggered-in height in respect of the output ducts for the signal A IFIG. 4 shows diagrammatically that the novel, differential pressureamplifier is essentially to be regarded as a pressure dividerarrangement with variable resistances R and R which are adjustedsimultaneously but in opposite directions by the difl'erence between theinput signals E and E The output signal A is measured between theresistances R and R and the output signal A, is measured between theresistances R and The qualitative progress of the pressure of outputsignals A, and A as a function of the difference between input signals Eand E is shown in FIG. 5. It is clear that with increasing differentialpressure, i.e.,

when the pressure E becomes greater than the pressure E the balls 4 aredisplaced downwardly by means of the diaphragm 6. As a result thereof,the lower ball exposes or opens up to an ever increasing extent theoutflow cross-section to the duct 9, while the upper ball 4 increasinglycloses the outflow cross-section in the duct 8. The output signal Atherefore changes in the same direction as the input signal E andtherefore rises (FIG. 5), while the output signal A in the exemplaryembodiment selected, in which the dimensions and hence also theresistance conditions are chosen to be of identical magnitude, decreasesin the same sense. FIG. 5 shows that, when the difference between outputsignals A, and A is measured, the input difference (E E is amplified bythe factor V.

The present invention provides for a type of construction extremelyeasily manufactured for a difiiit?2 nlaifu%i8583faail tii ,Siii up newpossibilities of application for pneumatic differential pressureamplifiers.

While I have shown or described several embodiments of the presentinvention, it is understood that the same is not limited thereto but issusceptible of numerous changes and modifications as known to thoseskilled in the art, and I therefore do not wish to be limited to thesedetails but intend to cover all such changes and modifications as areencompassed by the scope of the appended claims.

Whatlclaim is:

1. A differential pressure amplifier with a housing and with tworesilient walls delimiting two input pressure chambers on one side andserving as adjusting v means for an adjusting ball valve meanscontrolling the inlet and outlet of compressed air into and out of atleast one outlet channel, characterized in that the resilient walls areoperatively connected with two balls substantially of the same diameterdisplaceably arranged in a bore provided in the housing of the amplifiersaid two balls being adapted to contact each other within the bore, andin that a supply channel for the compressed air is disposedsubstantially tangentially aligned with the point of contact of theballs with each other within the bore at least one outlet channel beingprovided which terminates in the bore substantially at a distance ofhalf the diameter of a ball of the ball valve means from the supplychannel.

2. A differential pressures amplifier according to claim 1,characterized in that the bore for the balls is of substantiallyconstant diameter.

3. A differential pressure amplifier according to claim 1, characterizedin that the two balls abut against each other and are acted upon at theopposite sides thereof by the difi'erential pressures.

4. A differential pressure amplifier according to claim 1, characterizedin that a center line of the supply channel is disposed substantiallytangentially aligned with the point of contact of the balls, and that acenter line of the at least one outlet channel is arranged atsubstantially the distance of half the diameter of the ball of the ballvalve means from the center line of the supply channel.

5. A diflerential pressure amplifier according to claim 1, characterizedin that the balls of the ball valve means are disposed in a cylinderinserted into a bore of the housing, said cylinder being provided withlateral slots of increasing cross section in the direction of theoutflow.

' 6. A differential pressure amplifier according to claim 5,characterized in that the cylinder for one outlet channel is provided atboth sides with horizontal slots and in that the supply channel isdisposed at right angle to a center line through the outlet channels attheir point of communication with the horizontal slots.

7. A differential pressure amplifier according to claim 6, characterizedin that the bore for the balls is of substantially constant diameter.

8. A differential pressure amplifier according to claim 7, characterizedin that the two balls abut against each other and are acted upon at theopposite sides thereof by the differential pressures.

1. A differential pressure amplifier with a housing and with tworesilient walls delimiting two input pressure chambers on one side andserving as adjusting means for an adjusting ball valve means controllingthe inlet and outlet of compressed air into and out of at least oneoutlet channel, characterized in that the resilient walls areoperatively connected with two balls substantially of the same diameterdisplaceably arranged in a bore provided in the housing of the amplifier, said two balls being adapted to contact each other within the bore,and in that a supply channel for the compressed air is disposedsubstantially tangentially aligned with the point of contact of theballs with each other within the bore , at least one outlet channelbeing provided which terminates in the bore substantially at a distanceof half the diameter of a ball of the ball valve means from the supplychannel.
 2. A differential pressures amplifier according to claim 1,characterized in that the bore for the balls is of substantiallyconstant diameter.
 3. A differential pressure amplifier according toclaim 1, characterized in that the two balls abut against each other andare acted upon at the opposite sides thereof by the differentialpressures.
 4. A differential pressure amplifier according to claim 1,characterized in that a center line of the supply channel is disposedsubstantially tangentially aligned with the point of contact of theballs, and that a center line of the at least one outlet channel isarranged at substantially the distance of half the diameter of the ballof the ball valve means from the center line of the supply channel.
 5. Adifferential pressure amplifier according to claim 1, characterized inthat the balls of the ball valve means are disposed in a cylinderinserted into a bore of the housing, said cylinder being provided withlateral slots of increasing cross section in the direction of theoutflow.
 6. A differential pressure amplifier according to claim 5,characterized in that the cylinder for one outlet channel is provided atboth sides with horizontal slots and in that the supply channel isdisposed at right angle to a center line through the outlet channels attheir point of communication with the horizontal slots.
 7. Adifferential pressure amplifier according to claim 6, characterized inthat the bore for the balls is of substantially constant diameter.
 8. Adifferential pressure amplifier according to claim 7, characterized inthat the two balls abut against each other and are acted upon at theopposite sides thereof by the differential pressures.